The invention relates to a flexible bulk goods container.
Flexible bulk goods containers are used for packaging, transporting, handling and stockpiling different bulk goods materials in amounts of, in each case, 500 to 2,000 kg. However, they are also used in area, in which there are increased risks of explosion. These risks of explosion can be attributed, for example, to the risks associated with filling a bulk goods container (FIBC) with material capable of undergoing dust explosions. Moreover, when emptying the FIBC, the risk of gas explosions can arise in addition to the risk of dust explosions, if the material is emptied into a container, which already contains a flammable liquid. In all areas of use, in which there is the risk of explosion due to gases, vapors or dust, electrostatically conductive bulk goods containers must be used.
In the design of electrostatically conductive bulk goods containers, consideration must therefore be given to the risks of a brush discharge in the case of gases and vapors with a low minimum ignition energy, as well as to the risks of a sliding brush discharge, which is attributed particularly to charge double layers. In addition, electrostatic charging processes, such as those caused by the filling and emptying process, must of course, be taken into consideration. However, it is also necessary to make certain that the bulk goods container has strength properties, which ensure bulk goods up to 2 tons can be held and that there is sufficient tightness to prevent the exit of dust through the fabric.
Bulk good containers of the initially named type are known, for which there is basic weave, which are coated on the inside and in which electrically conductive metal conductors in the form of metallic threads are integrated, is used. It is a disadvantage of these bulk goods containers that they are not produced from a homogeneous material (polypropylene) and that they therefore cannot be recycled. In addition, the danger exists that the metallic conductor will react chemically with the bulk goods.
The European publication 0 413 886 discloses a bulk goods container, for which a basic weave of synthetic yarns and electrically conductive synthetic yarns, which are woven into the basic weave, are used. These electrically conductive synthetic yarns preferably are monofilaments, in which conductive carbon is dispersed, as it is in those yarns basically known for the fabrics of the British patent 2,101,559, as well as the German patent 25 24 640.
It is an important disadvantage of such a bulk goods container that, when yarns are used, be they in the shape of fibers, monofilaments or multifilaments, relatively small surface areas are available for discharging the electrical potential. If a particular surface size is to be provided for adequate discharging properties, the thread is exceptionally stiff and not sufficiently flexible, so that the strength properties in this respect are adversely affected at those places where the thread is woven into this fabric. Because of the different diameters of basic weave threads and the electrically conductive threads, defects in the finished fabric cannot be avoided and have a further adverse effect on the strength properties of the container. Moreover, the production of this known fabric is very expensive, because basic weave threads and electrically conductive threads cannot be processed with the same warp beam.